Capacity factors, soil sorption

Soil sorption is an important detoxification process for pollutants of aquifer waters however, sediment-column experiments to determine the soil sorption capacity are tedious, expensive and their results are affected by various extraneous factors. It was proposed to estimate the adsorption coefficients KA based on their correlation with the capacity factors, k, measured by isocratic RP-HPLC108. A QSAR estimation study was carried out of soil sorption coefficients, K0c, of polar organic chemicals such as substituted anilines and phenols, based on descriptors such as n-octanol-water partition coefficients, Kow,... 

The effect of soil properties on the adsorption of substances. Physical and chemical characteristics of adsorbing components in the soil also affect the binding capacity and stability of chemical substances in the soil. The particle size is a further important factor. Colloidal particles exhibit the largest sorption capacity, with a diameter of 10 to 10 mm. The sorption capacity decreases with increasing size, and particles larger than 2 mm in diameter essentially do not affect the soil sorption capacity. From the chemical standpoint the soil sorbents may be divided into two groups ... 

The sorption process (abiotic retention) is controlled by the concentration of phosphate in soil pore water and the ability of the solid phase to replenish phosphate into pore water. This can be described in terms of two regulating factors The intensity factor of the sorption process is controlled by the concentration of phosphate in soil pore water, and the capacity factor refers to the ability of the solid phase to replenish phosphate to the soil pore water. 

Barrow [772] derived a kinetic model for sorption of ions on soils. This model considers two steps adsorption on heterogeneous surface and diffusive penetration. Eight parameters were used to model sorption kinetics at constant temperature and another parameter (activation energy of diffusion) was necessary to model kinetics at variable T. Normal distribution of initial surface potential was used with its mean value and standard deviation as adjustable parameters. This surface potential was assumed to decrease linearly with the amount adsorbed and amount transferred to the interior (diffusion), and the proportionality factors were two other adjustable parameters. The other model parameters were sorption capacity, binding constant and one rate constant of reaction representing the adsorption, and diffusion coefficient of the adsorbate in tire solid. The results used to test the model cover a broad range of T (3-80°C) and reaction times (1-75 days with uptake steadily increasing). The pH was not recorded or controlled. 

There is little doubt that fertility- and productivity-affecting features of soils, such as liquid and electrolyte household management, i.e. the capacity to take up, hold, and pass liquids, ventilation, sorptional capacity, and the transport of dissolved substances, are highly dependent upon the structure and permeability of soil component colloid aggregates [1, 2]. Accordingly, the structure and permeability of mineral component clays are important factors [3]. 

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